Abstract: MicroRNAs (miRNAs) is a class of endogenous non-coding small molecule RNA. To analyze the biological function of Populus euphratica miR156j, miR156j precursor(peuMIR156j)was cloned and transferred into Arabidopsis thaliana, and 35S:MIR156j transgenic plants were obtained in the current work. The results showed that overexpression of miR156j increased the number of rosette leaves, leading to thick leaves and delayed flowering, which was similar to A. thaliana,rice, etc. P. euphratica miR156j conservatively played a main role in plant development. Also germination rate and growth condition of 35S:MIR156j transgenic A. thaliana under salt treatment were better than that of the wild type, and the expression assay of gene SPL6, SPL9 and SPL11 demonstrated the downregulation caused by miR156 Based on the predicted stressassociated target gene STRS2(stress response suppressor 2), we presumed that the molecular mechanism underlying the involvement of miR156 in salttolerance may be ascribed to the regulation of STRS2 expression.